When Yom Tov falls on Friday, one must set aside an Eruv Tavshilin – which consists of two cooked food items from before Yom Tov, usually some bread and a hard boiled egg – to allow him to cook and make preparations on Yom Tov for Shabbat.
The question arises as to whether one must prepare an Eruv Tavshilin if he does not intend to cook on Yom Tov for Shabbat. This question for example, is relevant to people who did all their cooking ahead of time, before Yom Tov, and will need only to warm the food before Shabbat. This question also applies to people who spend Yom Tov and Shabbat in a hotel or by a relative, and therefore do not need to prepare any food on Yom Tov for Shabbat. Must they make an Eruv Tavshilin?
This question was addressed in the work Ma'amar Mordechai (commentary to the Orach Chayim section of Shulchan Aruch by Rabbi Mordechai Karmi, 1749-1825), in Siman 527 (16). He writes that this issue hinges on the debate recorded there in the Shulchan Aruch as to whether one requires an Eruv Tavshilin to allow lighting the Shabbat candles on Friday afternoon (when Yom Tov falls on Friday). If candle lighting does, indeed, require an Eruv Tavshilin, then one must prepare an Eruv Tavshilin regardless of whether he intends to cook on Yom Tov for Shabbat. But if one may light candles on Friday afternoon without an Eruv Tavshilin, then he need not prepare an Eruv Tavshilin if he does not need to cook on Yom Tov.
The Ma'mar Mordechai rules that since this issue is subject to a debate among the authorities, in such a case, when one does not plan on cooking on Yom Tov, he should make an Eruv Tavshilin but without reciting the Beracha of "Al Mitzvat Eruv." He must recite the text designating the food as an Eruv Tavshilin ("Be'dein Eruva…"), which makes reference to lighting candles on Yom Tov in preparation for Shabbat ("U'le'adlukei Sheraga…"), but he omits the Beracha, since the requirement of Eruv Tavshilin in this case is subject to controversy. This is also the ruling of Chacham Bentzion Abba Shaul (Jerusalem, 1924-1998), in his work Or Le'tziyon (vol. 3, 22:6).
It should be noted that an Eruv Tavshilin permits not only cooking, but also other necessary preparations for Shabbat. For example, those in charge of the Sifrei Torah in the synagogue are allowed – through the Eruv Tavshilin – to roll the Sifrei Torah on Yom Tov afternoon to prepare them for the Shabbat Torah reading. Just as the Eruv Tavshilin allows one to make food preparations on Yom Tov for Shabbat, so does it allow one to prepare the Sifrei Torah in the synagogue on Yom Tov for Shabbat.
Summary: When Yom Tov falls on Friday, one must make an Eruv Tavshilin before Yom Tov to allow cooking and preparing on Yom Tov for Shabbat. If one does not intend to cook on Yom Tov for Shabbat, he should nevertheless prepare an Eruv Tavshilin before Yom Tov, though without a Beracha. An Eruv Tavshilin allows making other kinds of preparations on Yom Tov for Shabbat, as well, such as rolling the Sifrei Torah on Yom Tov to the place from where they will be read on Shabbat.
